Cristiano Ronaldo is in line for a morale-boosting return to the Portugal side for Tuesday's friendly in the United States against Ireland, just two days before the World Cup begins.

The 29-year-old forward has missed Portugal's previous two warm-up matches through injury, hindering their preparations for the Brazil tournament and sparking speculation that he might not be fit in time.

But the Real Madrid ace returned to training on Saturday with Paulo Bento's side, who have failed to sparkle in their captain's absence.

Portuguese officials were tight-lipped Sunday about Ronaldo's availability for the Ireland encounter, but forward Vieirinha told reporters: "If he is fit to train, he is fit to play the match."

Portugal face a daunting World Cup opener on June 16 against Germany in Group G, which also comprises the USA and Ghana.

Bento has been keen to stress that Portugal -- who only made it to Brazil via a play-off with Sweden that saw Ronaldo fire a hat-trick -- are more than just one player.